Conventionally, a motor which is used in a digital camera or the like has been known in which a lead screw is formed on its rotation shaft (see, for example, Japanese Patent Laid-Open No. 2006-129649).
As described in the above-mentioned Patent Reference, both ends of the rotation shaft of the motor are supported by bearings through a ball. The bearing supporting a shaft end on a rotor side of the rotation shaft is a cylindrical member which is made of resin. The bearing is inserted into a through-hole of a bearing holder made of resin which is fixed to a stator of the motor and the bearing is urged on a rotor side by a plate spring (urging member). Further, a recessed part (bearing part) is formed on an end face on the rotation shaft side of the bearing and a ball is fitted into the recessed part.
The bearing is designed so that the bearing is held within the through-hole of the bearing holder in a state that a prescribed minute clearance is maintained.
However, as described above, the bearing is formed of resin by injection molding. Therefore, when molding material is cooled and solidified in the molding step, deformation (shrinkage) may occur by contraction of the molding material. Especially, when inexpensive resin material is used, shrinkage having occurred becomes larger and thus cylindricality of the bearing is largely deteriorated. As a result, when the bearing having the above-mentioned shrinkage is fitted to the bearing holder, a clearance between the bearing and the through-hole of the bearing holder increases to cause a larger torque loss, or larger noise or vibration during rotation of the motor.